Fuel mixing control device



Jan. 8, 1957 J. R. DAVIS FUEL MIXING CONTROL DEVICE 2 Sheets-Sheeh 1 Filed Nov. 14, 1952 Bnvcntor J REX DAV/S Jan. 8, 1957 i DAVIS 2,776,821

FUEL MIXING CONTROL DEVICE FJ' 'led Nov. 14, 1952 2 Sheets-Sheet 2 VII/l J a i g F |\W 80 m: 79 !iiLr$':: 7,

United States Patent FUEL MIXING CONTROL DEVICE J. Rex Davis, Los Angeles, Calif.

Application November 14, 1952, Serial No.'320,375

21 Claims. (Cl. 26162) This application is a continuation-in-part of my prior application Serial No. 22,915, filed April 23, 1948, and now abandoned.

This invention relates to fuel and air mixing devices, and especially to carburetors for supplying a fuel and air mixture to internal combustion engines and the like. The apparatus shown herein as illustrative of invention includes an arrangement of fixed and movable passages or fluid paths, the relative positions, movement, and proportional areas of which provide the necessary characteristics for accomplishing the objects of this invention.

A number of fuel and air mixing devices have been heretofore devised and patented which were directed toward the general objective of providing a constant fuelto-air ratio in the mixture under widely varying demand conditions. Such prior attempts have not been uniformly successful, however, mainly because of the difference in densities of liquids and gases, and also because of the fact that no design factor has been provided to compensate for difierences in fuel density.

With a View to overcoming the defects above noted, it is a major object of the present invention to provide a device for proportioning the mixture of fuel and air for internal combustion engines which is so constituted as to maintain a relatively constant weight ratio over a wide range of varying velocities and pressures so long as the percentage of the maximum demand remains constant.

It is another object of the invention to improve the I homogeneity of the fuel-air mixture supplied to internal combustion engines.

It is still another object of the invention to provide apparatus of the class described in which the fuel-to-air ratio changes in accordance with the differing degree of throttle opening, providing for differing percentages of maximum demand.

Yet a further object of the invention is to provide, in apparatus of the class described, an arrangement of passages such as to deliver fuel in response to a composite pressure derived from a combination of the static pressures across the throttle and pressures created by the velocity of air passing specific parts of the throttle valve.

A still further object of the invention is to provide a degree of self-regulation of the pressures causing delivery of fuel into the main air passage, such self-regulation be ing accomplished by means of an inverse feedback effect as between the quantity of fuel delivered and the pressure causing such fuel delivery.

Another object of this invention is to secure a uniform distribution of the fuel throughout the entire cross section of the main air stream in its course to the engine.

Another object is to supply a mixture of fuel and air which will be maintained at a uniformly constant fuel-toair ratio over widely varying conditions of loads and speeds of the engine to which the mixture is supplied.

Another object is to maintain a constant fuel-to-air ratio under the same conditions of operation at widely varying altitudes.

Another object is to obtain the maximum atomization ice 2 of all liquid fuel by delivering all liquid fuel into the air stream at the position of its maximum velocity.

Another object of this invention is to so control the dififerential pressures across the one fuel control passage that a progressively increasing volume of fuel will be caused to flow therethrough as the volume of air passing the air control valve increases, irrespective of the differential pressure across the air control valve,-thereby eliminating the necessity of coordinating a diminishing supply of fuel feeding from one location with an increasing supply of fuel feeding from another location, as is done in many conventional devices for a similar purpose.

The foregoing and additional objects, advantages and features of this invention will appear from a perusal of the accompanying drawings, the subjoined detailed de-' scription, the'preamble of these specifications, and the appended claims.

It is believed that the following description of one of the preferred forms of the device will convey, to those versed in the art, all necessary information for the construction and useof the invention, but it is to be understood that the drawings and description thereof are not to limit the invention in any sense whatsoever except as specifically limited by the appended claims.

Figure 1 of the drawings is a vertical sectional view of one possible form of a fuel and air mixing device or carburetor in which the invention is shown;

Figure 2 is an elevational view of one side of the device which is preferably called the rear side;

Figures 3 and 4 are on a somewhat smaller scale, Figure 3 being'a top plan view of the device, and Figure 4 being a bottom plan view thereof;

Figure 5 is an enlargedview showing a portion of the carburetor taken substantially along line 5-5 on Figure l, but with the throttle inan altered position;

Figure 6 is a vertical sectional view taken substantially along line 6--6 of Figure 1;

Figure 7 is a vertical sectional view similar to Figure 6 but showing the throttle in fully opened position;

Figure 8 is a vertical section taken on line 88 in Figure l, with parts of float valve enlarged, which shows a float actuated fuel level control;

Figure 9 is a modified form of part of the invention in sectional view taken on line 6-6 of Figure 1 showing a modified throttle valve, prime numbers being used for indicating similar parts in the preferred form, and like numbers for indicating like parts in the preferred form; and

Figure 10 is a vertical sectional view of a modified fuel flow control passage, enlarged, wherein the prime numbers are employed for indicating similar parts in the preferred form, and like numbers for indicating like parts in the preferred form.

Referring to .the drawings, Figures 1 to 8 disclose one form of a mixing device embodying the invention in a downdraft carburetor for an internal combustion engine. The illustrated device includes a housing having a lower section 1 and an upper section 2, secured together by a plurality of cap screws 3, a suitable gasket 4 being placed between the two sections so as to form a fluid and gas tight seal.

The base section 1 includes a lower terminal flange 5" suitable for attachment to the intake manifold of an internal combustion engine (not shown), and has a tubular Wall 5 defining a central bore or passageway 6. Protruding walls 7 and 7' on the base section 1 provide a chamber 8 into which liquid fuel is delivered and controlled at the desired level 69 by the float 9. On the tubular wall 5 of base section 1, diametrically opposite to the chamber 8, is a boss 6' for increasing the bearing area for a transverse throttle shaft 31 and providing a stop for limiting the rotational movement of the throttle shaft. The boss 6 also provides a better anchorage for retaining the two main body sections 1 and 2 in alignment.

A portion of the tubular wall 5 adjacent the chamber 8 is thickened, and has formed therein a vertical passageway 18. It will be understood that while the walls forming the chamber 8 and the portion in which the vertical passageway 18 is formed are shown as integral With the base section 1, these elements may be separate from the base section and secured thereto by screws or other suitable means.

The upper sectionZ, includes a tubular wall it defining a central bore 11 and terminating in an enlarged an nular projection 14 for the attachment of a conventional air cleaner or other air supply (not shown). The wall 10 has a flange 104 formed therein adjacent its lower end which extends laterally to serve as a cover for the ,fuel chamber 8. The flange 104 is connected to the tubular wall 10 by a gusset member 10' having a diagonal passageway 10', the purpose of which is to equalize the gas pressures at the upper end of the body section 2 and in the fuel chamber 8.

The sections land 2 are held in proper alignment by dowel pins 3' and 107, the latter also serving as a closure plug for the top end of the fuel passage 18. Thus the bore 11 registers with the bore 6 to provide a straight annular passage of uniform cross sectional area. The total length of the bores 6 and 11 is approximately three times the diameter thereof and the upper and lower enlargements or flared sections of the bores 6 and 11 indicated at 12 and 13, are for the purpose of securing a gradual transition to the diameter of any passages with which the device may be connected. It is preferable that the angle of the flared walls at 12 and 13 with the axis of bores 6 and 11 be substantially 2630 since this produces a minimum of turbulence in the air flow through the bore 6-41. V

A throttle valve30 is mounted on the transverse shaft 31 in the bore 6 and is a modification of the conventional butterfly valve retaining only two of the usual characteristics; that of self-balancing and the rate of changing the opening of the passage. The valve isof a thickness substantially equivalent to /s of its diameter and the latter is substantially equal to the diameter of the bore The'central portion of the throttle valve 30 is a modified square section, from which mutually parallel wings 43 and 44, disposed in the respective planes of two opposite sides; project from each of two diagonally opposed corners of the squaresection.

The diameter of one portion of the cross bore indicated at 15" is substantially equivalent to the thickness of throttle valve and the diameter of the remaining portion indicated by 16 is sufficiently smauer'to' journally receive the throttle shaft 31 which in turn fits tightly in a diametral bore in the central body of the throttle valve 30. The cross bore is continued (to the left in Figure 1) with a somewhat reduced diameter, as indicated at33; to connect with' the upper end of the passage 18. The reduced bore section 33 receives a tube1 7, the latter having a press fit or being threaded to p'rovidea liquidtight seal between tube'17 andthe bore 33. The tube'17' serves to convey liquid'fuel from passage 18 to some distance into an axial bore 32 in throttle shaft 31, and may also serve as a restrictor to provide ther'equi'red relative cross sectional areas of passage 18 and the passage into the tube at their point of juncture.

A sleeve surrounds the throttle shaft 31 at the righthand end thereof as shownin Figure 1, and is journally received in the cross bore at 15. The sleeve 35 is secured to the throttle shaft 31 by any suitable means such as brazing or welding, at the right h'and end thereof (see Figure l), at which point a throttle control lever is also attached to the shaft and sleeve. Such brazing or welding also prevents any leakage of air between the sleeve 35 and shaft 31. The sleeve 35 'is drivingly engaged with the throttle valve 30 by means of tooth-like projections 4 fitting into complementary recesses as indicated at 38. Thus the valve 30 is at all times maintained in a fixed position on the shaft 31.

The throttle valve control lever 40 is attached in a fixed relationship to throttle shaft 31, and it is provided with an adjusting screw 41 arranged so that it will contact the protrusion 6 on wall 5 when the thottle valve is in the correct position for the proper idling speed of the engine. The adjusting screw 41 permits a change of position of the valve for adjustment of the idling condition. The lever 40 is also provided with a hole or any other suitable means for the attachment of a conventional throttle control rod as indicated at 42. H

The bore 32 extends entirely across the interior of the throttle valve 30" and provides a' fuel chamber therein which chamber is communicated by a number of orifices 3-.- with the upstream surface of the valve 30 (when closed as in Figure 6). The cross sectional area of the bore 32 is equal to or slightly greater than the combined cross sectional areas of the multiple orifices 34. As can be seen best in Figure l, the orifices 34 arearranged along the length of the bore portion 32, and the depth of the latter is such as not to interfere with the free flow of air or fuel through any one of the orifices. A multiplicity of holes, symmetrically arranged relative to a central point, is provided in one side of the square section of the throttle valve as indicated by 52', see Figure 6; their number and lozatior being such that they coincide with orifices 34- in throttle shaft 31,when the two parts arcassembled together. Each of these holes 52 is slightly larger than its corresponding orifice 34 and is slightly chamfered at its outer end.

In addition to the multiple orifices 34, the bore portion 32 is communicated with the downstream surface of the throttle valve 30 (when closed) by a single orifice 36 through the wall of the shaft 31 at a point substantially from the point at which the multiple orificcs 34 are located. Diametrically opposite the single orifice 36 is a threaded hole receiving a screw 37 which also serves to prevent longitudinal movement of the throttle valve 30 on the shaft 31. A fuel atomizing and distributing unit 50 is affixed to the valve 30 by brazing or by some other suitable means, or may be formed as an integral part of the throttle valve, and has an internal passage aligned with the orifice 36.

Due to pressure relationships later to be described, fuel is delivered into the bore 32 through the tube 17 and a bushing 39 having a press fit in the bore 32 and a close rotating fit with the tube 17 provides a liquid tight seal at the mouth of the cross bore 32, whereby to provide a reservoir for the retention of a quantity of liquid fuel in the bore 32. In order to increase the capacity of the bore 32, the same may be formed with recessed grooves therein as indicated at 168 in Figure 1.

An important factor in the operation of the present invention resides in the shape of the throttle valve 30. Each of the wings 43and 44 is shaped as a segment of the same circle, thus cooperating when closed to substantially block the bore 6. The flat area of the wing 44 on the low pressure side of the throttle valve 30- is substantially a semi-circle, since a corner of the square central body adjacent the wing 44 is rounded off to leave a cylindrical surface 45 having a radius equal to substantially /2 of the thickness of the throttle valve.

The fiat area of the upstream throttle wing 43 is somewhat difierent thanthat of the downstream wing 44 and is greater than a semi-circle, due to the fact that the corner of the square central body section adjacent the upstream wing is not rounded off in the same manner as that adjacent the downstream wing. The upstream exposed corner of the central body of the throttle 30 is rounded off so as to leave two oblique cylindrical surfaces 47 and 48, each having aradius equal to /2 of the thickness of the throttle. The axes of the two cylindrical surfaces 47 and 48 are angularly disposed to the diametral axis of the throttle valve 30 so that at the center of the central body, the square section is unmodified, as indicated at 46 in Figures 5, 6 and 7. Thus the area of the upstream wing 43 is a portion of a circle bounded by an arc of substantially 180 and by two chords of said circle intersecting at an apex at the point 46.

The atomizing unit i) carried by the valve 30 extends normally to, and such a distance from the downstream surface that a cross passage 51 therein will occupy a position substantially in the center of the air stream passing the throttle valve (see Figure 7) When the latter is full open. The projected area of the unit 50 should preferably be substantially the same as the projected area of the triangular shaped portion of the upper surface of the throttle valve formed by the small cylindrical surfaces 47 and 48 meeting at the apex 46.

The end of the central body of the valve 30, diametrically opposite the sleeve 35, is formed as a spherical surface having a radius equal to the radius of bore 6, so as to permit rotation of the throttle valve in the bore 6 about the transverse axis.

As the throttle valve 30 is opened from the position shown in Figure 6 to the position shown in Figure 7, the manifold suction causes air to pass downwardly through the passageway 6 dividing and passing around the valve 30 on both sides thereof. In this connection, it will be noted that the cross sectional area of that portion of the passageway which lies to the left of the valve 30 (in Figure 6) and thus extends past the holes 52, is varied in its cross sectional area due to the arcuate movement of the apex 46. During the initial 45 of opening movement, the clear area of the passageway to the left of the valve 30 and above the axis thereof is reducing due to the encroachment of the point 46 thereinto, and from 45 to 90 such area is increasing due to the withdrawal of the point 46 therefrom. Such variation in the cross sectional area of the air passageway is an important factor to the operation of the invention as will be described hereinafter.

The details of the liquid fuel control are shown in Figures l and 8, wherein it will be seen that the float 9 has a pair of arms 66 which are pivoted at 61 to the body of the device, and carries a valve contact arm 62 having a curved end 63 adapted to make contact with the bottom end of a fuel valve 64 and raise and lower same. An offset bore 65 is formed in the flanges and has secured therein a threaded bushing 66 having an annular valve seat 67, the opening through which is adapted to be opened and closed by the lowering and raising of the valve 64. A conduit (not shown) is connected to the duct or bore 68 for Supplying liquid fuel to chamber 8 of the device when the float 9 falls below a predetermined certain level. All the passages associated with the valve 64 are of such sizes relative to the passage 18 and other fuel delivery passages as to maintain the liquid fuel level indicated at 69.

In Figure 9 is shown a modified throttle valve 30 which has a relatively thin flexible plate 70 coinciding in shape and dimensions with the underside of the upstream wing 43' thereof. This plate is attached to the wing close to the central square section of the throttle valve by means of the rivets 71 or in some other suitable manner which allows the outer periphery of the plate to bend away from the wing 43'. A set screw 72 is threaded into a through bore of the wing 43, contacts the flexible plate 70 and provides a means of adjusting the effective thickness of the outer periphery of this wing. By increasing the thickness of the edge of the wing, a lag in the degree of opening of the passage on this side of the throttle valve is caused to occur, and this causes an increased percentage of the air to be effective on the holes 52 to increase the flow of fuel, as will be described in detail later herein. The effectiveness of the plate 70 is limited almost entirely to the initial opening of the throttle valve and therefore constitutes means for minor adjustmentof the fue1- to-air ratio at and near the idling positions of the throttle valve. Note that thetransverse bore of the form of the valve shown in Figure 9 may be off center, that is, eccentric to the extent of the distance indicated by x in said figure.

An orifice 74 through wing 44' may be employed to obtain fuel flow characteristics similar to those obtained by use of the flexible plate 70. The effective action of the orifice 74 is maintained through a greater degree of throttle valve movement, and its use effects a change in the fuel metering characteristics of orifice 36 producing a richer mixture during the initial throttle opening, with a gradually decreasing effect as the throttle opening is increased. Another possible refinement consists in an orifice 75 through the screw 37 to provide a leaner mixture during low part throttle operation, with a gradually increasing fuel-to-air ratio as the throttle opening is increased. Each of the foregoing modifications may be employed separately or in any desirable combination.

In Figure 10 is shown a modified fuel flow control unit wherein the plug 107 located in the upper end of liquid fuel passage 18 is replaced by a longer plug 107' having formed therein an axial passage 79 connecting with equal area transverse passage therein, the mouth of which abuts the liquid fuel supply tube 17. A small channel 76 is cut into the side of the plug 107 adjacent the mouth of the passage 80 and the lower end of the channel is communicated with the axial bore 79 by an orifice 78. The modification of Figure 10 thus involves a plurality of branch fuel passages but no change in the total effective cross sectional area of said passages, as compared to the previous embodiment. Also this construction permits of changing the total area of the fuel orifices without disturbing the main body section of the device. I have found that good results are obtained when the cross sectional area of the adjoining passages 79 and 80 is substantially 30 percent less than the total required area, and the cross sectional area of the supplementary orifice 78 is such that the total effective area is percent. The orifice 78 serves to convey fuel from the main fuel passage into channel 76, from which it passes through a space 77 between one wall of the channel 76 and the end of tube 17' into the enlarged bore of said tube 17' thereby permitting a more constant supply of a small quantity of fuel to reach orifice 36, for discharge through the unit 50 when the fuel demand is very small.

For a general description of the operating characteristics of the carburetor, first assume a substantially closed, idling position for the throttle valve 30. Starting of the engine produces a usual manifold vacuum on the engine side of the throttle valve 30, causing air to flow through the valve entering at the upstream multiple ports 34 and discharging through the orifice 36 and the atomizing unit 50. At this point, it should be noted that if the orifices 34 were entirely closed, the full manifold vacuum would be applied through the orifice 36 to the top of the fuel column in the passage 18, thus drawing fuel through the bore 32 and out the orifice 36 at a theoretical maximum rate. If, on the other hand, the aggregate cross sectional area of the orifices 34 were made so large as to present substantially no resistance to air passing therethrough, no vacuum would be produced within the bore 32 and thus no fuel would be drawn up through the fuel passage 18.

The size of the orifices 34 is such, however, that their restrictive effect is between the above theoretical limits, producing an appreciable pressure drop across the orifices 34 due to the flow of air therethrough. From the foregoing, it will be seen that the degree of suction applied to the fuel column in the passagels is equal to the pressure drop across the orifices 34, since the pressures on the upstream side of the orifices 34 and on top of the fuel in the chamber 8 are substantially equal, due to the inter-communicating diagonal passageway 10". The justmentioned suction or pressure differential causes fuel to rise up the column 18 and pass transversely through the tube 17 into the bore 32 within the throttle valve 30.

From this point, the fuel discharges downwardly through the orifice36 being admixed with air which is also passing through the orifice 36 as previously described.

The rate of delivery of liquid fuel into the bore 32 is self-regulatory due to the negative feedback effect of the liquid fuel on the orifice 36. When the liquid fuel reaches the orifice 36, the stream delivered therethrough reduces its capacity to discharge air and thus reduces the velocity of air drawn through the multiple orifices 34. A reduction in such velocity reduces the pressure drop across the orifices 34 and thus reduces the pressure differential or suction applied to the fuel column 18. This in turn reduces the rate of liquid fuel delivery. Such self regulation continues until the rate of fuel delivery is stabilized at a value required for normal idling.

The quantity per second of liquid fuel of a given density that acts on the orifice 36 to establish the abovementioned stabilized condition is dependent on various factors including the total area of the orifice 36, the aggregate area of the orifices 34, the differential pressure existing across the throttle valve, and the static and fric tion heads resisting the flow of the liquid fuel up the column 18 and through the transverse tube 17. All of these values may be established and coordinated in the structure shown, by calculations of a character later to be described. Such coordination achieves a substantially constant fuel-to-air ratio irrespective of the opening of the throttle for any given engine rate.

Having noted the operating conditions at the idling position of the throttle, now assume that the throttle valve be opened by rotating the same counterclockwise. Such rotation, it will be noted, has the effect during the initial of rotation, of increasing the restriction caused by the arcuate movement of the apex 46 toward the wall of the bore 6, and at the same time moves the multiple orifices 34 downstream from such increasing restriction. The overall effect of the changes just mentioned is to increase the rate of air flow through the bore 6 and at the same time increase the degree of suction or differential pressure produced within the bore 32, thus increasing the rate of fuel delivery. At this point, it should be noted that the restrictive effect of the cylindrical surfaces 47 and 48 and the apex 46 is not at any given instant, the same on all of the orifices 34.

Rotation of the throttle valve 30 also has the effect of changing the position of the internal openings of the orifices 34 and 36 in the bore 32. The openings of the orifices 34 move gradually toward the lowermost position in the bore 32, while the orifice 36, initially at the lowermost point, moves upwardly during the throttle opening rotation. Thus the orifices 34 are initially air influx ports producing the required pressure drop to regulate the delivery of liquid fuel, and at some point in the rotation of the valve 30, change their function to that of fuel discharge ports as they change their relative position with respect to the restrictions in the bore 6. The discharge of fuel through the ports 34 is believed to be due to the velocity head created by the air passing down through the bore 6 past the restriction of the surfaces 47 and 43 and the apex 46. As previously described, the conversion of the orifices 34 from air influx ports to fuel discharge ports is not simultaneous, but occurs at a different point in the rotation, for each of the respective orifices, depending upon the location of the particular orifices 34 with respect to the center of the valve 30.

In the advanced stages of operation, there will be a substantial quantity of liquid fuel entrained in the bore 32. In the event of a need for sudden acceleration, reflected in a quick depression of the accelerator pedal, thus opening the throttle valve 30 to the position shown in Figure 7, the above-mentioned entrained body of fluid will be dumped through the ports 34as the latter are quickly shifted to positions projecting downwardly from "the bore 32.

It will be noted that the opening rotation of the throttle valve 30 not only moves the orifices 34 downwardly, but moves the outermost end of the atomizing unit 50 in an arcuate path to ultimately assume the position shown in Figure 7 wherein the discharge end of the port 36 is substantially in the center of that branch of the air passage passing to the right of the valve 30. This arrangement effects a discharge of fuel from both the orifices 34 and the orifices 36 when the throttle is at or near full open position, and produces a marked improvement in the uniformity of distribution of fuel across the interior of the bore 6.

Having described the operation of the unit in general terms, consideration is now given to the manner in which the proper proportions of the various passages and orifices are determined. In order to achieve the stated objects of the invention, it is desirable that the dimensions of the passages and orifices in any particular carburetor embodying the invention be selected in accordance with the piston displacement and compression ratio of the engine to which the device is to be applied. ln such design, particular attention is directed to the dimensioning of the orifice 36 and its cooperating orifices 34 in conjunction with the changing areas of the air passage 6, directly influenced by the protruding valve portion 46.

The diameter of the main air passage 6-41 is selected to produce a given pressure drop in passing through the two segmental areas lying on opposite sides of the throttle shaft in the open position of the throttle valve for a given air demand of the engine for which the carburetor is designed. l have found that for an air demand equal to the total suction stroke piston displace ment per second of a given engine when rotating at a speed of 400 R. P. M., the diameter of the passages should be such that the aforementioned pressure drop will be equivalent to a ninety foot head of air at standard conditions. In this connection, 1 have found it convenient to express all pressures as an equivalent head of air, and hereinafter the term air head is used to designate such equivalent head of air.

I have also found that the fuel level in the float chamber should be adjusted to lie below the throttle shaft axis a distance such that the static pressure differential of the fuel at the two levels mentioned is approximately sixteen feet air head.

I have further found that the effective cross sectional areas of each of the passage 18 and the passage through the tube 17 should be selected to produce a pressure drop of forty-nine feet air head when delivering the quantity of fuel required to obtain the desired fuel-to-air ratio for an air demand equal to the total suction stroke piston displacement per second of the engine at 400 R. P. M. and under standard conditions of pressure and temperature.

Having determined the diameter of the main air passage 6, 11, the fuel level in the float chamber and the effective cross sectional area of the passage 18 and the passage through the tube 17, the effective area of the orifree 36 may then be determined as follows.

Step 1.Determine the volume of fuel required to provide the desired fuel-to-air ratio when combined with twenty percent of the total volume of air (that is, the air demand represented by the total suction stroke piston displacement per second of the engine at 400 R. P. M. under standard conditions of temperature and pressure).

Step 2.--Deterrnine the crosssectional area of a stream of fuel delivering the volume determined in Step 1, when flowing at a velocity equal to that which would be caused by a pressure differential equal to the difference between standard atmospheric pressure and the initial pressure in the combustion chamber when a volume of air equivalent to twenty percent of one displacement of the pistonhas been permitted to enter the cylinder during a suctionstroke.

Step 3.-Make the area of orifice 36 approximately eighteen times the cross sectional area of the fuel stream found in Step 2.

The area of the orifices 34 may be determined as follows.

Step 1.Multiply by three the pressure that would be required to cause the correct velocity of flow of fuel through a horizontal passage having a cross sectional area equivalent to the predetermined cross sectional areas of the passage 18 and the passage through tube 17 to deliver into the bore 32 of throttle shaft 31 the quantity of fuel required for the predetermined idling mixture. Add to the last-mentioned product the pressure equivalent to the head of fuel represented by the distance from the fuel level in the float chamber to the axis of the throttle shaft, and determine the velocity of air required to provide a velocity head equal to the sum so obtained.

Step 2.Determine,the air volume required to be passed by the orifices 34 in the following manner.

Intermediate Step A.-Determine the percentage of cylinder charge of air required by the engine to idle at 400 R. P. M. Taking the volume of air in cubic feet which is equivalent to the last-mentioned percentage of the maximum air demand in cubic feet of the engine at 400 R. P. M., determine the degree of throttle opening required to permit this volume of air to pass per second at the velocity which would be caused by the differential pressure occurring across the throttle valve under the aforementioned condition.

Intermediate Step B.-Assuming the throttle valve position determined by Intermediate Step A, determine the velocity head of air occurring through the area between the wall of passage 6 and the adjacent surfaces 47 and 48, and consider this velocity head as a static head.

Intermediate Step C.-Assuming the same throttle valve position, determine the velocity head of air occurring through the area of the segment between the juncture of wing 44 and the square section of the throttle valve (the point 42') and the adjacent wall surface of passage 6.

Intermediate Step D.-Subtract from the total differential pressure occurring across the throttle valve (see Intermediate Step A) the sum of the static head as determined by Intermediate Step B plus the velocity head determined by Intermediate Step C, to determine a net available pressure.

Intermediate Step E.Determine the net available air passage area of orifice 36 by subtracting from the total area thereof, the area required to deliver the quantity of fuel required for the predetermined idling mixture (see Step 1).

Intermediate Step F.-From the net available air passage area of orifice 36 as determined by Intermediate Step E, and the net available pressure as determined by Intermediate Step D, compute the volume of air in cubic feet per second that would be passing through orifice 36.

Step 3.-Determine the area required to pass the volume of air determined by Step 2, when flowing at the velocity determined by Step 1. This area is the aggregate area of all of the orifices 34, and should be divided substantially equally among the number of such orifices employed. The number of orifices selected should be symmetrically disposed on either side of the center of the throttle valve.

The above described calculations, it will be realized, are not strictly rigorous, since they depend to large extent upon empirically determined constants and coefficients, and do not take into account the oft encountered difference between the effective and actual areas of passages and orifices. The calculations are nevertheless sufliciently precise to permit one skilled in the art to construct a device utilizing the principles of my invention which will provide an actual fuel-to-air ratio closely approaching the predetermined values upon which the calculations are based. Final dimensions for obtaining the fuel-to-air ratio sought may then be ascertained by appropriate minor adjustment of the dimensions in accordance with the principles herein stated, and/or by use of the adjustment means hereinbefore described with reference to Figures 9 and 10.

It is, of course, understood that various changes and modifications may be made in the details of form, style, design, and construction of the whole or any part of the specifically described embodiment of this invention without departing from the spirit thereof; such changes and modifications being within the scope of the following claims.

I claim:

1. In a carburetor having a housing defining a vertically extending down-draft passage, a valve unit including a central body rotatably mounted in said passage on a horizontal axis, and a pair of wings disposed in parallel planes offset from said axis on respective sides thereof, said body being rotatable through an angle of substantially from closed to open positions and having a fuel receiving and dispensing chamber and a plurality of radial ports communicating with said chamber, said ports being disposed, in the closed position of the valve, with one of the ports extending downwardly substantially parallel with the axis of said passage and another extending laterally on that side of the body which moves downwardly in the opening movement of the valve, whereby in the movement of said valve to open position, said one port will swing upwardly to extend horizontally, transverse to the axis of said passage, and said other port will swing downwardly to extend downwardly, parallel to the axis of said passage.

2. In a carburetor having a housing defining an air passage, a valve unit including a central body rotatably mounted in said passage on a horizontal axis, and a pair of wings disposed in parallel planes offset from said axis on respective sides thereof, the spacing of said planes being substantially equal to one-third the diameter of said passage, said body being rotatable through an angle of 90 from closed to open positions and having, on that side which moves downwardly in the opening movement of the valve, a side face substantially normal to and extending between said parallel planes, said side face being disposed at a distance from the axis of said valve unit less than one-half the radial difference from said axis to the tip of the adjacent wing, said body having a fuel receiving and dispensing chamber and a plurality of radial ports communicating with said chamber, said ports being disposed, in the closed position of the valve, with one of the ports extending downwardly substantially parallel with the axis of said passage and another extending horizontally toward, and opening into, said side face, whereby said other port will extend downwardly in the opening position of the valve.

3. In a carburetor having a housing defining an air passage, a valve unit including a central body rotatably mounted in said housing on a horizontal. axis, and a pair of wings disposed in parallel planes offset from said axis on respective sides thereof, said body having lateral surfaces substantially perpendicular to said planes, a fuel receiving and dispensing chamber, and a plurality of radial ports communicating with said chamber, said ports, in the closed position of the valve, being in communication, one with a point located substantially central of the surfaces of said valve unit on the low pressure side of said body and the other with a segmental recess between said lateral surface of said body and the adjacent wall of said air passage on the high pressure side of said body.

4. A valve unit as defined in claim 3, including an adjustable plate on one of said wings, for changing the thickness of the edge of said one wing.

5. A valve unit as defined in claim 3, including a fuel atomizing unit communicating with said one port and projecting radially from the body, and a projection on the body generally opposite said unit.

6. A valve unit as defined in claim 3, wherein said body has, on its side opposite said one port, a projection which moves toward the adjacent wall of said passage in the initial opening movement and away from said adjacent wall in the final opening movement of said valve, increasing and decreasing respectively the velocity head between said projection and said adjacent wall.

7. A valve unit as defined in claim 3, wherein the center of said body is located on said axis of rotation.

8. in a carburetor, a housing defining an air passage, a fuel chamber adjacent to said air passage, a vertical fuel passage having one end terminating adjacent the floor of said fuel chamber and the other end terminating at a common terminus with one end of a horizontal fuel passage leading from the top end of said vertical fuel. passage into said air passage, said fuel passages meeting at an angle of substantially 90 and having equal cross sectional areas for some distance from their common terminus, and a valve comprising a body rotatably mounted in said housing within said air passage on a horizontal axis and having a chamber communicating at one end with said horizontal fuel passage, and a pair of wings projecting in opposite directions from said body, said wings being disposed in parallel planes and offset from said axis on respective sides thereof, said body having, on that side which moves downwardly in the opening movement of the valve, :1 side face extending transversely between said planes and disclosed at a distance from said axis less than one-half the distance from said axis to the tip of the adjacent wing, said body having radial fuel ejection ports communicating with said chamher, said ports being arranged, in the closed position of the valve, with one of said ports extending horizontally and opening into said side face and the other extending downwardly, substantially parallel to the axis of said passage.

9. A carburetor as defined in claim 8, wherein said air passage has a frusto-conical inlet portion the wall of which is inclined at an angle of substantially 2630 to the wall of the body of said passage.

10. A carburetor as defined in claim 8, wherein said air passage includes a frustum shaped inlet portion the wall of which is inclined at an angle of substantially 2630 to the wall of the body of said passage, and wherein said housing has a passage extending from said inlet portion to the top of said float chamber.

ll. A carburetor as defined in claim 8, wherein said housing has a channel parallel to said vertical fuel passage adjacent the upper end thereof and a pair of vertically spaced ports of different areas extending from said ver ical fuel passage to said channel, said channel communicating with said horizontal passage.

12. in a carburetor having a housing defining an air passage, a valve unit including a central body rotatably mottnted in said air passage on a horizontal axis, and a pair of wings disposed in parallel planes offset from said axis on respective sides thereof, said body having a Fuel receiving and dispensing chamber and a plurality of radial ports communicating with said chamber, said ports, in the closed position of the valve, being in communication, one with the low pressure side of said body and the other with the high pressure side of said body on its side opposite said one port, a projection which moves toward the adjacent wall of said passage in the opening movement of said valve, increasing the velocity head between said projection and said adjacent wall, said projection being defined between a face of said body which constitutes an extension of an outer face of one of said wings. and a lateral face of said body extending from the other wing to meet said first mentioned face. generally at right angles thereto.

l3. In a carburetor having a housing defining an air passage, a valve unit including a central body rota-tably mounted in said air passage on a horizontal axis, and a pair of wings disposed in parallel planes offset from said axis on respective sides thereof, said body having lateral surfaces substantially perpendicular to said planes, a fuel receiving and dispensing chamber, and a plurality of. radial ports communicating with said chamber, said ports, in the closed position of the valve, being in communication, one with a point located substantially central of the surface of said valve unit on the low pressure side of said body and the other with a segmental recess between said lateral surface of said body and the adjacent wall of said air passage on the high pressure side of said body, said body being journaled eccentrically in said housing with the center of said body displaced from said axis.

14. In a fuel mixing control device, a housing defining a vertical air passage, a fuel chamber alongside said passage, a vertical fuel passage leading upwardly from said fuel chamber, the upper end of said vertical passage terminating at a common terminus with one end of a horizontal fuel passage leading from said common terminus into said air passage, said fuel passages meeting at an angle of substantially 90 and having equal cross sectional areas for some distance from their common terminus, and a valve comprising a body rotatably mounted in said housing within said air passage on a horizontal axis and having a chamber communicating at one end with said horizontal passage and a pair of wings projecting in up posite directions from said body, said body having, on that side which. moves downwardly in the opening movement of the valve, a side face substantially normal to and extending between said parallel planes, said side face being disposed at a distance from the axis of said valve unit less than onehalf of the radial difference from said axis to the tip of adjacent wing, said body having radial fuel ejection ports communicating with said chamber, said ports being arranged in the closed position of the valve, one of said ports extending horizontally and opening into said side face and the other extending downwardly parallel to the axis of said passage, and a fuel atomizing unit in communication with said downwardly extending port, said atorntzing unit having a chamber and a cross passage so constructed and arranged that fuel and air passing therethrough will be directed into the airstream passing the ends of said Wings.

15. In a carburetor having means defining an air passage: a butterfly valve rotatably mounted on a transverse ms in said passage, said valve having formed therein; a chamber, a first port leading from said chamber to a downstream surface in said valve when closed, a plurality of second ports leading from said chamber to spaced points in the upstream surface of said valve when closed, said points being disposed in said upstream surface to move downstream when said valve is opened, and a portion offset from said axis and positioned to move into said air passage to progressively constrict the same above successtve ones of said second ports as said valve is opened; and supply means to deliver fuel to said chamber.

16. In a carburetor having means defining an air passage a butterfly valve rotatably mounted on a transverse axis 111 said passage, said valve having formed therein; a chamber, a first port leading from said chamber to a downstream surface in said valve when closed, a second port leading from said chamber to an upstream surface of said valve when closed, and an arm projecting substantrally radially downstream from said axis when said valve s closed, said arm being disposed on said valve to swing nto a transverse position in said passage when said valve is opened, the exterior opening of said first port being in the distal end of said arm; and supply means to deliver fuel to said chamber.

17. In a carburetor having means defining an air passage: a butterfly valve rotatably mounted on a transverse axis in said passage, and having its wings offset into sub stantially parallel planes on respective sides of said axis, the wing moving upstream when said valve is opened being upstream of said axis when said valve is closed, said valve having formed therein; a chamber, a first port leading from said chamber to a downstream surface in said valve when closed, a second port leading from said chamber to an upstream surface of said valve when closed, the exterior opening of said second port being located in a portion of said upstream surface joining the proximal edges of said wings; and supply means to deliver fuel to said chamber.

18. In a carburetor having means defining an air passage: a butterfly valve rotatably mounted on a transverse axis in said passage, and having its wings ofiset into substantially parallel planes on respective sides of said axis, the wing moving upstream when said valve is opened being upstream of said axis when said valve is closed, said valve having formed therein; a chamber, a first port leading from said chamber to a downstream surface in said valve when closed, an arm projecting substantially radial-- ly downstream from said axis when said valve is closed, said arm being so disposed on said valve to swing into a transverse position in said passage when said valve is opened, and a second port leading from said chamber to an upstream surface of said valve when closed; the exterior opening of said first port being in the distal end of said arm; and supply means to deliver fuel to said chamber.

19. In a carburetor having means defining an air passage: a valve body mounted on a transverse axis in said passage, having a substantially coaxial chamber on said axis and adapted for limited rotation through substantially 90 about said axis; two radial fuel passages having ports in said chamber so disposed therein that one or the other fuel passage selectively extends downstream from said chamber at the respective limits of said rotation; a pair of wings on said body extending transversely therefrom to close said air passage at one of said limits of rotation, the one of said wings which moves downstream when said body is rotated from said closed position being offset downstream from said axis whereby to communicate one of said fuel passages to the upstream side of said body to act as an air passage when said valve body is in said closed position; and supply means to deliver liquid fuel into said chamber.

20. In a carburetor having means defining an air passage: an air valve in said passage movable between open and closed positions therein, said valve having substantial thickness whereby to restrict a stream of air through said passage to a substantial degree irrespective of the position thereof; means defining a liquid fuel chamber adjacent said passage having a port discharging into said passage to deliver liquid fuel thereinto; means forming a second port in said chamber aifixed to move with said valve from a position communicating said chamber with a point in said passage upstream of the restriction of said valve when closed to a position communicating said chamber with a point in said passage downstream of said restriction when said valve is open; a third port in said chamber positioned to extend downstream when said valve is closed and across said stream when said valve is open; and means to deliver liquid fuel into said chamber.

21. The construction of claim 20 further characterized by having a plurality of said second ports all affixed to said valve for concurrent movement therewith and so disposed with respect to each other and said valve that said second ports successively pass from a position upstream to a position downstream of said restriction as said valve is opened.

References Cited in the file of this patent UNITED STATES PATENTS 1,132,314 Eiker Mar. 16, 1915 1,305,744 Rhoads June 3, 1919 1,319,789 Newcomb Oct. 28, 1919 1,321,471 Phillips Nov. 11, 1919 1,325,688 Burr Dec. 23, 1919 1,383,044 Weiland June 28, 1921 1,477,280 Pordes Dec. 11, 1923 2,035,191 Reynolds Mar. 24, 1936 2,190,314 Firth Feb. 13, 1940 FOREIGN PATENTS 510,346 France Sept. 3, 1920 

